Limescale removal compositions

ABSTRACT

Limescale removing compositions are disclosed which comprises a C1-C6 linear or branched alkyl sulfonic acid or mixtures thereof. Said alkyl sulfonic acids are particularly efficient in removing limescale and they are furthermore stable to bleach/oxidants. Therefore, compositions can be formulated which further comprise acid-stable oxidant compounds. Also, mixtures of alkyl sulfonic acids and sulfamic acid are particularly effective in removing limescale. The compositions of the invention are used to remove limescale from a variety of surfaces.

TECHNICAL FIELD

The present invention relates to compositions for the removal oflimescale. The compositions herein can be used on a variety of surfaces,ranging from bathrooms and kitchen surfaces to various appliances. Thecompositions herein can further be used to remove limescale fromdentures.

BACKGROUND

Tap water always contains a certain amount of solubilized ions whicheventually deposit as salts, on surfaces in contact with said water, asit evaporates. Such salts include calcium carbonate, commonly referredto as limescale. This phenomenon of limescale accumulation on surfaceswhich are often in contact with water may damage surfaces and affect thefunctioning of taps or appliances. Also, the accumulation of limescalein the toilet bowls is aesthetically unpleasant and favors thedeposition of further soil and the growth of microorganisms. It istherefore important to control this limescale accumulation phenomenon.

A variety of compositions have been proposed for this purpose, whichtypically comprise various acids, such as hydrochloric acid. However,compositions of the art formulated with said acids require a significantamount of acid to ensure effective removal of limescale, and are thuspotentially harmful to the user in case of contact with the skin, oraccidental ingestion. It is thus an object of the present invention toprovide limescale removing compositions which are particularly efficientin removing limescale, yet which have a lower reserve of acidity thanthe compositions of the art, thus which are less harmful.

It is also desirable to formulate compositions which comprise bleaches.Indeed, bleaches possess many desirable properties, includingdisinfection properties. Furthermore, such compounds as monopersulfuricacid are particularly effective as disinfectants and in removing and ordecolouring stains for household cleaning applications (copendingEuropean patent application EP 93870198.4). However, bleaches in generalraise compatibility issues in relation with the acids used to removelimescale. In particular, persulfuric acid is not compatible with theacids used in the art to remove limescale because persulfuric acidoxidizes the limescale removing acid upon storage, resulting in adramatic loss of available oxygen. And by the time the product reachesthe consumer, most of the available oxygen is lost. Typical acids usedin the art for removing limescale, namely maleic, citric, hydrochloricand sulfamic acid are all oxidized by persulfuric acid in particular. Itis thus an object of the present invention to provide a limescaleremoving composition which can be formulated with bleaches, inparticular persulfuric acid, in a stable manner.

In response to these objects, we have now found that such a limescaleremoving composition could be formulated which comprises, as the acid, aC1-C6 linear or branched alkylsulfonic acid, or mixtures thereof.

SUMMARY OF THE INVENTION

The present invention thus encompasses a composition suitable forremoving limescale, which comprises from 1% to 50% by weight of thetotal composition of a C1-C6 linear or branched alkylsulfonic acid, ormixtures thereof. In one embodiment of the invention, the compositionsof the present invention preferably comprise an acid-stable bleachcompound. In another embodiment of the invention, the compositionsherein additionally comprise a small amount of sulfamic acid. In itsbroadest embodiment, the present invention further encompasses the useof aqueous compositions comprising a C1-C6 linear or branchedalkylsulfonic acid, or mixtures thereof, for removing limescale.

DETAILED DESCRIPTION OF THE INVENTION

The compositions of the present invention are aqueous liquidcompositions comprising a C1-C6 linear or branched alkylsulfonic acid,or mixtures thereof. Particularly preferred for its limescale removalperformance is the use herein of methanesulfonic acid which iscommercially available for example from Aldrich, William Blythe & Co.Ltd. or Elf Atochem. The compositions herein comprise from 1% to 50% byeight of the total composition of said acid or mixtures thereof,preferably from 1% to 30%, most preferably 1% to 20%. The compositionsaccording to the present invention are less has than the compositions ofthe art in that at parity limescale removal performance the reserve ofacidity is much less than the compositions in the art. Thus in thisrespect, in case of contact with the user's skin or in case ofingestion, the compositions of the present invention will be lessharmful.

The pH of the compositions according to the present invention may rangefrom 0 to 4, preferably 0 to 2, and is essentially determined by thetype and amount of acid used.

In one embodiment of the present invention, the compositions herein maycomprise an acid-stable bleach i.e., an oxidant compound. Byacid-stable, it is meant herein a compound which is stable in the acidicenvironment of the compositions herein. This criterion is to be assessedon a case by case basis, depending on the specifics of givenformulations. It is essential that the bleach/oxidant chosen be stableat the pH of the formulation being considered. By stable, it is meantherein that the oxidant should preferably not undergo more than 30% lossof available oxygen in 6 months at room temperature (25° C.). A widevariety of oxidants have been described in the art which are suitablefor use herein. Suitable acid-stable oxidant compounds for use hereininclude inorganic and organic peroxides. Examples of inorganic peroxidesare: hydrogen peroxide and sources thereof (e.g., perborate.percarbonate), persulfate salts (i.e., dipersulfate and monopersulfatesalts), persulfuric acid and mixtures thereof. Examples of organicperoxides are: benzoyl peroxide, organic percarboxylic acids (i.e.,peracetic acid) and mixtures thereof. Percarboxylic acids and, ingeneral, organic or inorganic peroxides can be either solubilized in theformula or dispersed in the form of suspended solids or emulsifiedliquids. Particularly preferred for use herein are hydrogen peroxide orsources thereof, and persulfuric acid or salts thereof because of theirexcellent stain removal performance and stability in acidic matrices,and mixtures thereof.

Preferred salts of persulfuric acid for use herein are monopersulfatesalts, commercially available as Curox® from Interox. The compositionsherein may comprise from 0.1% to 50% by weight of the total compositionsof said acid-stable bleach/oxidant compound or mixtures thereof,preferably from 1% to 30%, most preferably 1% to 20%.

In another embodiment of the present invention, the compositions hereinmay comprise a small amount of sulfamic acid. Indeed, we have found thatthe combination of the alkylsulfonic acids herein together with sulfamicacid act in synergy in removing limescale. This property is particularlyinteresting as it allows the formulation of compositions which areparticularly effective in removing limescale, while they comprise onlyminor amounts of sulfamic acid, thereby reducing harshness. Accordingly,the compositions herein may comprise from 0.1% to 25% by weight of thetotal composition of sulfamic acid, preferably from 0.1% to 20%, mostpreferably from 0.2% to 15%. The synergistic effect observed depends tosome extent on the ratio of sulfamic acid to alkylsulfonic acid.Preferably, the ratio of sulfamic acid to alkylsulfonic acid should beof from 1:6 to 1:3. In this embodiment where sulfamic acid isincorporated in the compositions herein, it is preferred to formulatethe compositions without monopersulfuric acid and similar oxidants,since monopersulfuric acid oxidizes sulfamic acid, thereby resulting inloss of available oxygen.

The compositions herein may further comprise surfactants since they areoften used on items or surfaces which have soils or stains which do notcomprise limescale, and which require the presence of surfactants in thecompositions of the present invention, in order to be removed from saidsurfaces. Thus the compositions according to the present invention cancomprise any surfactant, cationic, anionic, nonionic and zwitterionic,in amounts ranging up to 50% by weight of the total composition,preferably from 1% to 30%. Suitable anionic surfactants include alkyl oralkylene sulfates or sulfonates, alkyl or alkylene ether sulfates orsulfonates, linear alkyl benzene sulfonate and the like. Suitablecationic surfactants include quaternary ammonium salts. Suitablenonionic surfactants for use herein include ethoxylated carboxylic acidsand fatty alcohol ethoxylates. For example, when the compositions hereinare formulated so as to be used on inclined surfaces, it may bedesirable to formulate them as emulsions of nonionic surfactants, suchas in copending European patent application 9387009.1. Indeed,appropriate selection of the nonionic surfactants allows to obtaincompositions with pseudoplastic profile which leads to excellentspreading and clinging characteristics.

The present invention can further comprise a multitude of optionals suchas solvents, colorants, dyes, perfumes, stabilizers and the like.

EXAMPLES

The following compositions are made which comprise the followingingredients in the following proportions (total weight %)

    ______________________________________                                        Example 1                                                                     ______________________________________                                        Dobanol @ 91-10           2.1                                                 Dobanol @ 91-2.5          4.9                                                 Methanesulfonic acid      5                                                   Curox @                   6                                                   Cyclohexane               0.5                                                 water and minors (e.g., dye, perfume) up to 100%                              pH = 0.5                                                                      ______________________________________                                    

    ______________________________________                                        Example 2                                                                     ______________________________________                                        Dobanol @ 91-10           1.8                                                 Dobanol @ 91-2.5          4.2                                                 Methanesulfonic acid      10                                                  water and minors (e.g., dye, perfume) up to 100%                              pH = 0.3                                                                      ______________________________________                                    

    ______________________________________                                        Example 3                                                                     ______________________________________                                        Dobanol @ 23-2            6                                                   Dobanol @ 45-7            6                                                   Dobanol @ 91-10           3                                                   Methanesulfonic acid      5                                                   Hydrogen peroxide         9                                                   water and minors (e.g., perfume, dye) up to 100%                              pH = 0.5                                                                      ______________________________________                                    

    ______________________________________                                        Example 4                                                                     ______________________________________                                        Dobanol @ 91-10           2.1                                                 Dobanol @ 91-2.5          4.9                                                 Methanesulfonic acid      5                                                   water and minors (e.g., perfume, dye) up to 100%                              pH = 0.5                                                                      ______________________________________                                    

    ______________________________________                                        Example 5                                                                     ______________________________________                                        Methanesulfonic acid      5                                                   water and minors (e.g., perfume, dye) up to 100%                              pH = 0.5                                                                      ______________________________________                                    

    ______________________________________                                        Example 6                                                                     ______________________________________                                        Dobanol @ 91-10           1.8                                                 Dobanol @ 91-2.5          4.2                                                 Methanesulfonic acid      5                                                   Curox @                   3                                                   Hydrogen peroxide         6                                                   water and minors (e.g., perfume, dye) up to 100%                              pH = 0.5                                                                      ______________________________________                                    

    ______________________________________                                        Example 7                                                                     ______________________________________                                        Dobanol @ 91-10           1.8                                                 Dobanol @ 91-2.5          4.2                                                 Ethanesulfonic acid       5                                                   Cyclohexane               0.5                                                 water and minors (e.g., perfume, dye) up to 100%                              pH = 0.7                                                                      ______________________________________                                    

    ______________________________________                                        Example 8                                                                     ______________________________________                                        Dobanol @ 91-10           1.8                                                 Dobanol @ 91-2.5          4.2                                                 1-propanesulfonic acid    10                                                  Cyclohexane               0.5                                                 water and minors (e.g., perfume, dye) up to 100%                              pH = 1                                                                        ______________________________________                                    

    ______________________________________                                        Example 9                                                                     ______________________________________                                        LAS                       10                                                  methanesulfonic acid      5                                                   water and minors (e.g., perfume, dye) up to 100%                              pH = 0.5                                                                      ______________________________________                                    

    ______________________________________                                        Example 10                                                                    ______________________________________                                        Dobanol @ 91-10           1.8                                                 Dobanol @ 91-2.5          4.2                                                 Methanesulfonic acid      7.5                                                 Sulfamic acid             2.5                                                 water and minors (e.g., perfume, dye) up to 100%                              pH = 0.3                                                                      ______________________________________                                    

    ______________________________________                                        Example 11                                                                    ______________________________________                                        Dobanol @ 91-10           1.8                                                 Dobanol @ 91-2.5          4.2                                                 Methanesulfonic acid      9                                                   Sulfamic acid             1                                                   water and minors (e.g., perfume, dye) up to 100%                              pH = 0.2                                                                      ______________________________________                                    

    ______________________________________                                        Example 12                                                                    ______________________________________                                        Dobanol @ 91-10           1.8                                                 Dobanol @ 91-2.5          4.2                                                 Methanesulfonic acid      5                                                   Sulfamic acid             5                                                   water and minors (e.g., perfume, dye) up to 100%                              pH = 0.4                                                                      ______________________________________                                    

The limescale removal efficiency of samples is evaluated by putting ablock of 6 g of calcium carbonate in 50 mls of the sample to beevaluated for a period of 30 minutes. The block is weighed dry beforeand after the experiment. We have measured that with composition 4, theweight decrease was 0.83 g and 1.1 g for composition 5. In the samecomposition, where methanesulfonic acid is replaced by the same weightquantity of sulfamic acid, the weight decrease is only 0.731 g. We havealso measured that it takes 13% of hydrochloric acid in a productmarketed under the trade name of WC Net @ to obtain a similar result(weight decrease 0.84 g) as with 5% methanesulfonic acid. Also,composition 10 illustrates that mixtures of alkylsulfonic acids withsulfamic acids are particularly effective in removing limescale. In thesame experiment, we measured a weight decrease of 1.06 g withcomposition 10, while the same composition but with 10% methanesulfonicacid (composition 2) only, instead, gave 0.87 g decrease, and the samecomposition but with 10% sulfamic acid only, instead, gave 0.85 gdecrease. Thus when combining the alkylsulfonic acids of the presentinvention with sulfamic acid, a better performance is obtained with athe same total amount of acid than with either of these acids alone. Thesynergistic effect of mixtures of sulfamic acid with alkylsulfonic acid,in this case methanesulfonic acid, is maximized at certain ratios.Composition 11 and 12, outside the preferred ratio range, give a weightdecrease of respectively 0.90 g and 0.93 g. This performance is betterthan the performance obtained with either acids alone but poorer thanthe performance obtained with composition 10 comprising a mixture ofbeth acids within the preferred ratio range.

In terms of reserve of acidity, we have measured that it takes 1.88 gNaOH/100 g product to bring composition 1 to pH4, while it takes 16.80 gNaOH/100 g product to bring to pH 4 a composition marketed under thetrade name WC Net @. Similarly, it takes 15.5 g NaOH/100 g product tobring to pH 4 a composition marketed under the trade name Harpiclimescale Remover @. Thus composition 1 has much less reserve of acidityand is therefore less harmful to the user.

In terms of bleach stability, the available oxygen is monitored incomposition 1. The available oxygen is measured in the freshcomposition, and in the same composition after one week storage at roomtemperature (25° C.). We have measured there was no loss of availableoxygen with composition 1 whereas in the same compositions wheremethanesulfonic acid was replaced respectively by the same amount(eight) of sulfamic or hydrochloric acid, the loss of available oxygenin the same period ranges between 66% and 98%. Thus the compositionsaccording to the present invention are much more stable

What is claimed is:
 1. An aqueous acidic composition suitable forremoving limescale, said composition comprising from 1% to 50% by weightof the total composition of a C1-C6 linear or branched alkylsulfonicacid, or mixtures thereof and from 0.1% to 25% of sulfamic acid.
 2. Acomposition according to claim 1 wherein said composition furthercomprises an acid-stable oxidant compound, or mixtures thereof.
 3. Acomposition according to claim 2 wherein said oxidant is hydrogenperoxide or a salt of persulfuric acid.
 4. A composition according toclaim 1 which further comprises up to 50% by weight of the totalcomposition of a surfactant.
 5. A composition according to claim 1, 2,or 3, wherein said composition comprises from about 0.2% to about 15% byweight of the total composition of sulfamic acid.
 6. A compositionaccording to claim 5 wherein the ratio of sulfamic acid to alkylsulfonicacid is from about 1:3 to about 1:6.
 7. A method of removing limescaledeposits from surfaces by contacting said limescale with an aqueouscomposition which comprises from 1% to 50% C₁ -C₆ linear or branchedchain alkyl sulfonic acid and from 0.1 to 25% sulfamic acid.